Graphene is a two-dimensional lattice of carbon atoms and is the basic structural element of many carbon materials including graphite, charcoal, carbon nanotubes and fullerenes. Graphene-based electronic devices have significant potential for achieving high performance in the electronic and semiconductor industry because of their unique electronic properties, which are complemented by excellent mechanical and thermal properties.
However, in order to realize the potential of graphene as a superior electronic-material, there is a need to develop a method of chemically modifying graphene while minimizing disruption of its conjugated π-electron clouds, particularly its high π-electron cloud density and its relatively un-scattered motion, which contribute to the superior properties of graphene. One solution is to make a covalent modification, which just rearranges the π-electrons of graphene, does not create any sp3 carbon centers at the reaction site and utilizes only the π-electrons derived from the conjugated graphene structure for filling the vacant metal orbitals.
Recent attempts to covalently modify graphene, in order to introduce a bandgap in its gapless semiconducting structure, have included either decoration of its macromolecular backbone with various organic functionalities (non-stoichiometric modification), such as the grafting of aryl groups to graphene, or making stoichiometric derivatives of graphene, namely graphane or fluorographene. However, these methods have involved the conversion of sp2-hybridized carbon atoms to sp3-hybridized configuration, leading to a serious disturbance and discontinuity in the conjugation of the π-electron clouds and thereby reducing the mobility of the carriers.
Moreover, pentahapto (η5)- and hexahapto (η6)-complexation was attempted but not achievable for fullerenes. In particular, the curvature in C60 significantly inhibits the potential of the molecule to function as a ligand in pentahapto-(η5), and hexahapto-(η6) complexation reactions, because the fullerene π-orbitals are directed away from the metal as a result of the rehybridization of the ring carbon atoms. In C60 the π-orbital axis vectors are directed away from the center of the respective rings and make angles of 16.3° (POAV2) to a normal to the plane of the five-membered rings and 25.8° (POAV2) to a normal to the plane of the six-membered rings. Thus, hexahapto-(ι6) coordination is even more strongly disfavored than pentahapto-(η5) complexation. The organometallic chemistry of fullerene is dominated by dihapto (η2)-complexation reactions.
Thus, methods and systems for providing for more effective and reversible covalent electronic modification of extended periodic π-electron carbon systems such as graphene, without disturbing the structural integrity of the sp2 hybridized carbon atoms, are desirable.